1. Field of the Invention
This invention relates to an apparatus and method for delivering paper stock to a paper machine More specifically this invention relates to apparatus including a preliminary moving wiremesh belt to which the stock is projected under pressure from above. Spaced down the wire-mesh belt is means for removing the drained stock from the belt and bridging it over to the paper machine. The invention also relates to the method of projecting a paper stock down onto a moving wire-mesh belt to create a shearing effect that makes a high-quality paper product.
In some versions of the invention the belt is moving and the projector is stationary; in other versions the belt may be stationary and the projector may be moving. Similarly, the projector may aim the stock in the direction opposite the movement of the belt; in others the projector may be aimed in the same direction.
2. Description of Related Art Including Information DisClosed Under .sctn.1.97 & 1.99
On the inlet side of a paper machine there have been various head-box designs to form the paper sheet on the wire-mesh belt or "wire belt" or "wire" as it is called in the trade. These headbox designs are traditionally divided into the following main classes:
(a) low pressure head-boxes PA1 (b) high pressure head-boxes PA1 multilayer head-boxes PA1 high-turbulence head-boxes PA1 controllable multi-channel head-boxes PA1 bunch tube head-boxes PA1 step diffuser head-boxes PA1 step flow head-boxes PA1 converflow head-boxes PA1 manifold tubes PA1 impact plates/turbulence plates PA1 perforated rollers PA1 flow chambers PA1 lip units PA1 control and measuring instruments PA1 the prevention of the stock/fiber agglomeration PA1 the creation of proper conditions for a defect-free sheet formation PA1 the conversion of the (turbulent) pipeline-flow into an evenly spread stream which can be applied onto the wire PA1 the stock variation along the paper machine (longitudinal) or across the paper machine PA1 all sorts of paper specifications in a wide range PA1 agglomeration of fiber PA1 foaming PA1 restrictions of paper machine speeds PA1 uncontrolled behavior and adjustment difficulties PA1 capacity problems PA1 corrosion
These were then developed into a multitude of semi- or fullhydraulic designs, such as
in which all of some basic details are almost the same, e.g.
The well-known technical characteristics are then adjusted to get the stock flow (of pulp etc. fibers) under good control. Notwithstanding this it is anyway impossible to reach a consistent optimum functioning because of the variations in the process conditions and the temperamental nature of the various designs. This has led head-box designing to become more an art than a science, an art in which the structure is not necessarily based on facts but on traditions.
New head-boxes were often developed only for the purpose of creating a new design category with total absence of any underlying sensible reason.
At any rate, the main purposes of the head-box or any other sheet former are the following e.g.
In spite of the elaborate conventional head-box designs, several difficulties arise due to the inability at the head-box itself (or in the so-called short circle, including pipeline with screeners and hydra-cleaners) to deal with various factors:
(With regard to capacity problems, the speed of a modern paper machine is usually between 200 . . . 1600 m/min. In higher machine speeds the head-box has always been a limiting factor, the faults in the sheet formation caused by the head-box cannot be repaired at the paper machine.)
The prior art has not really come to grips with these problem areas.